StorageLink Storage

August 17, 2018

Important: StorageLink technology has been removed from XenServer version 6.5 and higher. Applications, code, or usage that depend on StorageLink technology will not function in XenServer version 6.5 and higher. For information about migrating existing virtual disks (VDIs) from a StorageLink SR to an iSCSI or Fibre Channel SR, see CTX141433.

StorageLink SRs use storage adapters to access different storage arrays on all common storage technologies including both NAS and SAN over either Fibre Channel or iSCSI. The features available on a given StorageLink SR depend on the capabilities of the underlying array. StorageLink SRs can co-exist with other SR types on the same storage array hardware, and multiple StorageLink SRs can be defined within the same resource pool.

Depending on your environment and goals, StorageLink provides three advantages:

StorageLink SRs use the storage management software to access the storage.

StorageLink simplifies the storage configuration process. For example, when you create a StorageLink SR from XenCenter, StorageLink automatically creates the LUN, volume, and initiator group for you. This means that you do not have to go in to the storage management software to create these objects. However, you do need to have created an aggregate before you run the XenCenter SR wizard.

Every VDI created gets its own LUN. All StorageLink SRs use a LUN-per-VDI model where a new LUN is provisioned for each virtual disk (VDI).

By default, the XenServer block device-based storage inserts a Logical Volume manager on a disk, either a locally attached device (LVM type SR) or a SAN-attached LUN over either Fibre Channel (LVMoHBA type SR), iSCSI (LVMoISCSI type SR) or SAS (LVMoHBA type SR). When you use StorageLink to configure an SR, LUNs are directly mapped to virtual machines as VDIs. As a result, the array storage abstraction matches the VDI storage abstraction, which is helpful in environments that manage storage provisioning at an array level.

Note: StorageLink SRs are not supported with XenDesktop.

Methods of Creating StorageLink SRs

There are two methods of creating StorageLink SRs: allowing StorageLink to create the volume (default) or creating the volume in advance. The default method of creating SRs with StorageLink may not be optimal in all environments.

StorageLink-created Volumes (Default)

The standard (default) method of creating SRs with StorageLink is to select an aggregate in the SR creation wizard and then allow StorageLink to create the volume and LUN for you automatically. When you use this method, each VDI gets a LUN in a unique volume. However, in environments that want to create many VDIs, this may not be ideal since you can end up with numerous volumes. Some storage vendors have a maximum recommended limit of number of volumes per storage array. Likewise, when you create an SR with StorageLink, the volume names are auto-generated so they are not easy-to-read or meaningful, which can complicate management. This method also limits your ability to use deduplication to reduce space consumed by common data (such as operating systems or applications) in the volume.

Pre-created Volumes

The best practice method of creating SRs with StorageLink is to specify a previously created volume by selecting the Show All button in the XenCenter SR wizard. This method enables each virtual disk to get a LUN; however, you do not end up with numerous volumes with non-meaningful names.

Specifying a previously created volume when using the StorageLink SR wizard to create an SR simplifies volume management and administration. In this situation, each VDI gets a LUN in the selected volume. However, you do not end up with excessive, potentially unmanageable numbers of volumes (that is, one for each VDI). Using this method enables you to create a high number of VDIs. You can also create a more user-friendly meaningful name for the volumes, rather than the auto-generated names. This method also provides more efficient storage because it enables you to use deduplication since virtual disk images that share common data, such as the same operating system or application, may be stored in the same volume.

Creating StorageLink SRs for NetApp Arrays

When StorageLink creates an SR (and the associated LUN and volume), StorageLink automatically creates the initiator group with the Linux operating system. Manually configuring initiator groups with other operating systems is not recommended.

To create a Fibre Channel SR using StorageLink, you should have an iSCSI license on the storage during the initial discovery phase of the NetApp storage controller or be running ONTAP 8.1. If neither one of these apply, create the SR by using the standard SR creation process (without StorageLink) as described in Creating a New SR.

Note: To use StorageLink to connect to a NetApp storage array, you must enable httpd on the storage array before using the XenCenter New SR wizard.

To create a StorageLink SR

Open the New Storage Repository wizard: click New Storage on the toolbar.

Alternatively:

On the Storage tab for the selected pool or server, click New SR.

On the Storage menu, click New SR.

In the Resources pane, select a server or pool then right-click and click New SR on the shortcut menu.

Select StorageLink technology as the physical storage type and then click Next.

On the Name page, enter the name of the new SR. By default, a description of the SR will be generated automatically by the wizard, including a summary of the configuration options you select as you progress through the wizard. To enter your own description, clear the Auto-generate description check box and type in the Description box.

Click Next to continue.

On the Storage Adapter page, select one of the available storage system adapters and then click Next to continue.

On the Storage System page, select the storage system that will host the storage for this SR:

In the Array target box, enter the host name or IP address of the array management console.

Under Credentials , enter the username and password to use for connection to the array management console.

Click Discover to scan the target array for storage systems. After discovery has completed, select a storage system from the Storage System list, then click Next to continue.

On the Settings page, define the SR settings; the set of available settings for each new SR depends on the storage system vendor/model and the configuration of the storage pool you’ve selected.
| | |
|—————————–|————————————————————————————————————————————————————————————————|
| Storage pool | Identify the storage pool within the specified storage system to use for allocating storage. On some types of storage system you can use the Show all check box to list all storage pools here |
| RAID types | Select the level of RAID to use for the SR, as supported by the storage array |
| Provisioning type | Set the provisioning type (Default, Thick or Thin) |
| Provisioning options | Set the provisioning options (for example, deduplication) |
| Protocol | Set the storage protocol used to connect the managed server to the storage (iSCSI, Fibre Channel, or Auto to have the system choose) |
| Use CHAP authentication | If the server is configured to used CHAP authentication, select this check box and fill in the username and password to be used |

Click Finish to complete the new StorageLink SR configuration and close the wizard.

To create an SR and a LUN for Fibre Channel with StorageLink

In the XenCenter Resources pane, right-click the pool, and select New SR.

On the Array target box, enter the IP address for the storage controller. StorageLink initially communicates with the storage over IP.

In the Credentials section, enter the username and password for the storage and click Discover.

After the NetApp controller appears in the Storage system box, click Next.

On the Settings page, specify where and how you want the LUN configured:

From the Storage pool box, select the aggregate where you would like to create the LUN.

Note: NetApp does not recommend creating the LUN on the aggr0 aggregate, as this is reserved for system files.

In the RAID type box, select the RAID level you want the storage to use to format the LUN. RAID6 is the equivalent of the NetApp RAID-DP RAID type.

In the Provisioning type box, select either Thick or Thin provisioning. If you want storage to allocate space as it is used, select the Thin Provisioned check box.

In the Provisioning options box, select either None or Deduplication.

In the Protocol box, select Fibre Channel.

Click Finish to create the SR and the LUN. After StorageLink creates the SR and LUN, an SR appears in the Resource pane.

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